Utility Types – `Partial`, `Pick`, `Omit`, `Readonly`

The Standard Library Utility Types

Partial<T> – make all properties optional

type User = { id: number; name: string; };
type UserUpdate = Partial<User>;

Pick<T, K> – select a subset of keys

type UserName = Pick<User, "name">; // { name: string }

Omit<T, K> – remove keys from a type

type UserNoId = Omit<User, "id">; // { name: string }

Readonly<T> – all properties become read‑only

type ReadonlyUser = Readonly<User>;
// readonly id: number; readonly name: string;

NonNullable<T> – exclude null and undefined

type MaybeString = string | null | undefined;
type DefinitelyString = NonNullable<MaybeString>; // string